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CSA entry for 1e19
Original Entry
Title:
Transferase
Compound:
Carbamate kinase-like carbamoylphosphate synthetase
Mutant:
No
UniProt/Swiss-Prot:
P95474-P95474
EC Class:
2.7.2.2
Other CSA Entries:
Overview of all sites for 1e19
Homologues of 1e19
Entries for UniProt/Swiss-Prot: P95474
Entries for EC: 2.7.2.2
Other Databases:
PDB entry: 1e19
PDBsum entry: 1e19
UniProt/Swiss-Prot: P95474
IntEnz entry: 2.7.2.2
Literature Report:
Introduction:
Carbamoyl phosphate (CP) can be synthesised from mixtures of ATP, bicarbonate and ammonia by two types of enzymes: carbamoyl phosphate synthases (CPS) and carbamate kinases (CK). CPS uses a three step mechanism and consumes two molecule of ATP per molecule of CP synthesised; this reaction is essentially irreversible and is the first committed step in the biosynthesis of pyrimidines, arginine and urea. By contrast, carbamate kinases (CK) make CP reversibly in a one-step reaction using one molecule of ATP per CP molecule synthesised. The actual substrate for these enzymes is carbamate which is in equilibrium with bicarbonate and ammonia.

The in vivo role of CK from many organisms in which it has been studied (such as Enterococcus faecalis) seems to be to generate ATP from ADP using carbamoyl phosphate derived from the catabolism of arginine. However in some species, such as the hypothermophilic archaea Pyrococcus furiosus and Pyrococcus abyssi the enzyme appears to have an anabolic role. The enzyme from these species has in fact been called a "carbamate kinase-like carbamoyl phosphate synthetase", although studies have shown that is structurally and enzymologically a carbamate kinase.
Mechanism:
Phosphoryl transfer from ATP to carbamate or from CP to ADP is promoted by three lysine residues. In the direction of CP synthesis, Lys 277 is proposed to stabilise negative charge that develops on the ATP beta phosphate during the reaction. In the direction of CP breakdown, Lys 131 is proposed to have a similar role in stabilising negative charge that develops on the CP bridging oxygen as the product carbamate is formed. Lys 215 is proposed to interact with the gamma phosphate of ATP.
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Found by:
Literature reference 

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
LYSA 131 131Sidechain
ElectrostaticTransition state
In the direction of CP breakdown, is proposed to interact with the bridging oxygen atom of CP and neutralise the developing negative charge on this oxygen atom as the product carbamate is generated.
Evidence from paper Evidence concerns Evidence type
PubMed ID 10860751 Current protein Residue is positioned appropriately (ligand position hypothetical)
PubMed ID 11900534 Related protein: UniProt P0A2X8 Mutagenesis of residue
PubMed ID 10860751 Current protein Conservation of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
LYSA 215 215Sidechain
ElectrostaticTransition state
Proposed to stabilise negative charge in the transition state.
Evidence from paper Evidence concerns Evidence type
PubMed ID 10860751 Current protein Residue is positioned appropriately (ligand position hypothetical)
PubMed ID 10860751 Current protein Conservation of residue

ResidueChainNumberUniProt numberFunctional part FunctionTargetDescription
LYSA 277 277Sidechain
ElectrostaticTransition state
In the direction of CP synthesis, is proposed to interact with the terminal phosphate of ADP and neutralise the developing negative charge on this group as the product ADP is generated.
Evidence from paper Evidence concerns Evidence type
PubMed ID 10860751 Current protein Conservation of residue
PubMed ID 10860751 Current protein Residue is positioned appropriately (ligand position known)
References:
1
The 1.5 A resolution crystal structure of the carbamate kinase-like carbamoyl phosphate synthetase from the hyperthermophilic Archaeon pyrococcus furiosus, bound to ADP, confirms that this thermostable enzyme is a carbamate kinase, and provides insight into substrate binding and stability in carbamate kinases.
S. Ramón-Maiques and A. Marina and M. Uriarte and I. Fita and V. Rubio
J Mol Biol 299, (2) 463-76, (2000).
10860751
2
Molecular physiology of phosphoryl group transfer from carbamoyl phosphate by a hyperthermophilic enzyme at low temperature.
S. Ramón-Maiques and H. G. Britton and V. Rubio
Biochemistry 41, (12) 3916-24, (2002).
11900534
3
The carbamoyl-phosphate synthetase of Pyrococcus furiosus is enzymologically and structurally a carbamate kinase.
M. Uriarte and A. Marina and S. Ramón-Maiques and I. Fita and V. Rubio
J Biol Chem 274, (23) 16295-303, (1999).
10347186
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